Heat treating a fluid substance



u wmm mw www @wm Sm Gm fm d www 0.8m umm. www@ E L? ai w mw wmv Sm ANn w 8m`\\ QQ u Skv g M B 9 N w m M D 1 I l w m ,n s, s N. O A n m Km wm, s. n mmm. L nNu. D h. w N\\ b.. .Y u n c m .n T u Q Q3 n Q Q w m May 10, 1955 United States Patent O 1 2,707,991 HEAT TREATIN G A FLUID SUBSTAN CE Carl J. Lockman, Stockholm, Sweden, assignor to Rosenblad Corporation, New York, N. Y., a corporation of New York Application December 22, 1949, Serial No. 134,388 1 Claim. (Cl. 159-20) This invention relates to heat treating and more particularly to a method and apparatus for Vheat treating a fluid substance tending to deposit scale in a multiple stage system including a plurality of heat exchangers. In plants of this kind each heat exchanger has passages for conducting the said substance and a vaporized heating medium in heat exchange relation.

It is desired, in such plants, to interchange the paths of ow'of the uid to be treated and the heating medium through the heat exchangers so that, at predetermined intervals of time, the latter medium is conducted through the passages which during the preceding cycle havey served to conduct the fluid to be treated. In that manner, scale deposited from the iiuid during its ow in the latter passages will be dissolved and removed by the action of the vapor and condensate conducted through the same passages during the succeeding cycle so as to keep the heat exchanging surfaces clean. This rinsing method has proved to be very effective and practical but a disadvantage is that in largeplants the requisite changing valves for the supply of vapor will be very bulky and expensive.

It is therefore an object of this invention to enable an interchange of the paths of flow of the uid and the heating medium in a more simple manner and to reduce the number of the requisite valves to a minimum.

It is a further object of the invention to change periodically the order in which said uid to be treated and said heating medium are passed in succession from one heat exchanger to the other inthe system, and at the same time to interchange the paths of ilow of said uid and heating medium through the individual heat exchangers and also through the associated conduits, valves, pumps, etc.

A still further object of the invention is to reverse the direction of flow of the heating vapor and if desired also the dow of the said iluid through the system so as to alternate the first and last stages in the system, i. e. to cause the first heat exchanger in the series of stages to be the last heat exchanger in the succeeding cycle of operation, at the same time enabling an interchange of the passages of the uid and the heating medium in the individual heat exchangers without the necessity of providing changing valves in the inlets of the heating medium (vapor).

A further object of the invention is to provide a ash chamber intermediate each stage of the system and also an additional flash chamber connected to the first stage of the system and to enable the rst and the last ash chambers in the series of stages to be connected alternatively to a common inlet for heating vapor and to a common outlet for the exhaust vapor, if desired communicating with a condenser for the exhaust vapor.

It is also an object of the invention to reverse the ow of the heating medium simultaneously with reversing the path of flow of the fluid to be treated, for instance so as to apply the countercurrent principle in the heat exchangers in all operation stages of the system, and to provide valved interconnection conduits between the individual stages for this purpose.

Further objects and advantages of the invention will be apparent from the following description, taken in conjunction with the accompanying drawing, wherein the single ligure is a view partially in section diagrammatically illustrating the application of this invention to a multiple stage evaporation plant.' Parts of identical function are indicated by the same reference characters.

2,707,991 Patented May 10, 1955 The drawing illustrates as an example an embodiment of a multiple stage system for evaporating a fluid substance, with three heating stages, each comprising a heat exchanger 1, 2, and 3, respectively. Each heat exchanger has separate passages 4 and 5 for passing from the top to the bottom through one passage a vaporized heating medium in heat exchange relation with the uid substance which is passed from the bottom to the top through the other passage. A piping 10 connects a chamber or vessel 6 to the top of the passage 4 of the lirst heat exchanger 1 and a piping 16 connects said chamber 6 to the bottom of said passage 4. Through a piping 15 a chamber or vessel 9 communicates with the top of the passage 5 of the last heat exchanger 3 of the system. By means of pipings 11 and 12 a further chamber or vessel 7 is connected to the top of the passage 5 of the heat exchanger 1 and to the passage 4 of the heat exchanger 2, respectively. A piping 17a from the bottom of the passage 5 of the heat exchanger 1 and a piping 17b from the bottom of the passage 4 of the heat exchanger 2 are adapted alternatively to be connected to a piping 17 communicating with the chamber 7. For this purpose a three way valve 17e is provided in the piping system 17, 17a, 1'7b. In a similar manner pipings 13 and 14 connect a chamber or vessel 8 to the top of the passage 5 of the heat exchanger 2 and to the passage 4 of the heat exchanger 3, respectively, and a three way valve 18e is adapted alternatively to connect a piping 18 from said chamber 8 to either el' pipings 18a and 18!) communicating with the bottom of passage 5 of the heat exchanger 2 and with the bottom of passage 4 of the heat exchanger 3, respectively,

A pump 20a is provided in a piping 19a having a regulating valve 21a and adapted to interconnect the passages 4 of the heat exchangers 1 and 2. In a similar manner a pump 20h is provided in a piping 1911 having a regulating valve 21b and adapted to interconnect the passages 4 of the heat exchangers 2 and 3. There is also provided a pump 20c in a piping 19e having a regulating valve 21c and adapted to connect the passage 4 of the heat exchanger 3 to an outlet 22. Thus, these pipings 19a, 19h, 19C interconnect in series the passages 4 of the heat exchangers in the order l to 2 to 3 and nally to the outlet 22 from the plant. A piping 23a having a regulating valve 25a and a pump 24a interconnects the passages 5 of the heat exchangers 3 and 2, and a piping 23b with a regulating valve 25b and a pump 24b interconnects the passages 5 of the heat exchangers 2 and 1, while a piping 23e with a regulating valve 25e` and a pump 24e connects the passage 5 of the heat exchanger 1 to an outlet 26. Thus, the pipings 23a, 23b, and 23e interconnect in series the passages 5 of the heat exchangers in the order 3 to 2 to l and finally to the outlet 26 from the plant.

An inlet 27 to the plant with a pump 27a is connected to a three way valve 28 adapted alternatively to connect said inlet to either of two branch conduits 29a or 29h, of which the conduit 29a communicates with the passage 5 of the heat exchanger 3 while the conduit 29b communicates with the passage 4 of the heat exchanger l. As aforesaid the passage 5 of the heat exchanger 3 is con nected in series with the passages 5 of the heat exchangers 2 and 1 through the pipings 23a, 23b and 23e` While the passage 4 of the heat exchanger is connected in series with the passages 4 of the heat exchangers 2 and 3 through the pipings 19a, 19b, 19e.

A further inlet 30 to the plant is connected to a three v An outlet 33 from the plant is connected to a three way valve 34 adapted alternatively to connect said outlet 33 to either of the chambers 9 or 6 through branch conduits 35a and 351i, respectively.

A modification of the plant may be made by providing conduits 36a and 361: having valves 37a and 37b, rcspectively, and adapted to connect the piping systems 19a, 19b, 19t,1 and 23a, 23b, 23e with the tops of the passages 4 and 5 respectively.

In the operation of the plant now described and as suming that the valves 7c, 18e, 28, 31 and 34 are set in the positions shown in the drawing a diluted fluid substance (for instance sulphite waste liquor) is supplied from an external source and fed into the heating system through the inlet 27 and the piping 29a to the passage 5 of the heat exchanger 3 and from this passage through the pipings 23a and 23b to the passages 5 of the other exchangers 2 and 1.

A vaporized heating medium is supplied to the passage 4 of the heat exchanger through the inlet 30, the branch conduit 32a, the chamber 6 and the piping 10. In the heat exchanger 1 the heating vapor is condensed and the fluid substance supplied to the passage 5 of the same heat exchanger is heated and partially vaporized, causing a mixture of vapor and liquid to escape from the top of the passage 5 and to flow through piping 11 to chamber 7 in which vapor and liquid are separated and from which the liquid is returned to circulation through the piping system 17 and 17a to the bottom of said passage 5.

From chamber 7 the vapor is supplied as heating medium through piping 12 to passage 4 of the heat exchanger 2 in which an analogous heat exchanging process concerning the heating medium and the fiuid to be heated will take place similarly as described with reference to the heat exchanger 1. Vapor is passed from chamber 3 to the heat exchanger 3 in which said process is repeated once again and, finally, vapor is withdrawn from the chamber 9 and the heating system through the branch conduit 35a and the outlet 33. The piping 13, 18a serve as a circulation system similar to that provided by the piping 17 and 17a.

The concentrated fluid substance is withdrawn from the heating system through the outlet 26 by means of the piping 23C, the rate of withdrawal being regulated by valve 25e. The feeding of fiuid substance from stage to stage is regulated by valves 25a and 25h, respectively.

Condensate from the individual passages 4 is withdrawn from the outlet 22 through the piping system 19a, 19b and 19e, the flow through the individual conduits being regulated by the valves 21a, 2111 and 21C, respectively.

It will be understood that changing of the paths of flow according to the invention may be accomplished by operating five valves only for the whole plant, namely, by turning over the three-way valves 31, 34, 2S, 17e` and 18e from the positions shown so that the inlet 30 will be connected to the branch conduit 32b while the outlet 33 will be connected to the branch conduit 35]), the inlet 27 to the branch conduit 29h, and the pipings 17 and 18 will be connected to the pipings 1711 and 18h, respectively.

The result will be that not only are the paths of fiow of the heating medium and the heated fluid interchanged in each heat exchanger but also the position of the pressure stages and the temperature stages will be reversed so that the whole scheme of flow of the different media from one heat exchanger to the other will be changed in a mirror image relation, thus equalizing the working conditions which are apt to influence the degree of the tendency of deposition of scale. The sense of the expression mirror image relation may be explained by reference to an example. Assuming that during one cycle of operation one or both media are passed through a system of four stages l, 2, 3, 4 in the order 3-4-2-1, then a change of the order into a mirror image relation during the next cycle of operation will mean that the media will pass through the system in the 4 order 2-1-3-4. To arrive at this mirror image order one may imagine that the numeration of the series l, 2, 3, 4 be reversed into 4, 3, 2, 1 and that in this series the media be passed in the same numerical succession as during the first cycle. It will be appreciated that the result will be a new order 2-l34 as aforesaid.

lt will also be appreciated that on interchanging the paths of flow of the heating medium and the scale forn ing fluid not only the passages of the heat exchangers but also the feeding pumps and most parts ot the piping system of the plant will carry opposite media and benefit t" rom the scale dissolving properties of the condensate.

By-pass conduits 36a and 36b having valves 37a and 37b, respectively, may be connected between the pipings it) and 19a, 11 and 23C, 12 and 191:, 13 and 231i, 1.4 and 19C, 15 and 23a, respectively, to circulate condensate through the heating medium passages so as to strengthen the scale dissolving effect therein.

While the` drawing shows an installation by which the invention may be practised, it will be understood that the changing of the paths of fiow as described above is not limited to the operation of the device shown but may be accomplished by other modified means.

Whatl claim is:

A multiple stage heat treating system comprising a plurality of heat exchangers, for indirectly exchanging heat between a vaporized heating medium and a fluid substance tending to deposit scale, each heat exchanger having a first passage for conducting one of the heat exchanging media and a second passage for conducting the other of the heat exchanging media n heat exchange relation, a rst separation chamber having a top space connected to the top part of said first passage of the heat exchanger of one end stage in the system and a bottom space connected to the bottom part of the same passage, a further separation chamber intermediate each adjacent pair of stages of the system having a top space connected to the top part ot' the second passage of the preceding heat exchanger and also connected to the top part of the first passage of the succeeding heat exchanger, a bottom space in the latter separation chamber', pipe connections from said last mentioned bottom space to the bottom parts of the two last mentioned passages, means for alternatively connecting the pipe connections from said last mentioned bottom space to either of said two last mentioned passages, a last separation chamber having a top space connected to the top part of the second passage of the heat exchanger ot the other end stage in the system and also having a bottom space connected to the bottom part of the same passage, a first conduit system interconnecting the first passages of the individual heat exchangers, a second conduit system interconnecting the second passages of the individual heat exchangers. an outlet from each of said conduit systems, valved connections for alternate supply of the fiuid substance from an external source to the second or to the first passages of the heat exchangers, valved connections for alternate supply of vaporized heating medium from an external source to the first separation chamber or to the last separation chamber and valved connections for alternate with` drawing ot fluid substance vapour from the last separation chamber or from the first separation chamber.

References Cited in the file of this patent UNITED STATES PATENTS 936,760 Childs Oct. 10, 1911 1,005,600 Childs Oct. l0, 1911 1,582,066 Moore Apr. 27, 1926 1,582,067 Moore Apr. 27, 1926 2,012,668 Jahn Aug. 27, 1935 2,032,087 Goth Feb. 25, 1936 2,032,182 Oman Feb. 25, 1936 2,262,519 Talton Nov. l1, 1941 2,488,598 Lockman Nov. 22, 1949 2,490,750 Grewin et al. Dec. 6, 1949` 

